1. Field of the Invention
The present invention relates to a vehicle headlamp, and particularly to a projector-type vehicle headlamp having a variable light distribution function which is capable of changing a light distribution of the headlamp in accordance with a driving condition of a vehicle or the like.
2. Background Art
In general, a vehicle headlamp having a projector-type lighting unit is structured to reflect light from a light source disposed on an optical axis extending in a front and rear direction of a vehicle forward so as to be close to the optical axis using a reflector, and direct the reflected light toward the front of a lamp via a projection lens provided forwardly of the reflector.
When the projector-type vehicle lighting unit is structured as a vehicle headlamp for passing beam (low beam) irradiation, a shade for removing upward irradiation light by blocking a part of the reflected light from the reflector is provided between the projection lens and the reflector, whereby forward beam irradiation is performed in a passing beam light distribution pattern having a predetermined cutoff line.
In general, since the shade of the vehicle headlamp is stationary, when the shade is set for, e.g., the passing beam light distribution pattern, the lighting unit can be used only for the passing beam and, therefore, it is impossible to switch the lighting unit to the use for a running beam (high beam).
Accordingly, there is proposed a vehicle lighting fixture (vehicle headlamp) in which a shade is adapted to be a movable shade movable to a passing beam position and a running beam position, an upper end edge of the shade is positioned at a focal point of a projection lens when the shade is positioned at the passing beam position, and the upper end edge is appropriately moved out of the focal point of the projection lens when the shade is positioned at the running beam position, whereby optimum light distribution characteristics as the vehicle light fixture for the passing beam and for the running beam are obtainable (see, e.g., JP-A-2006-341696).
The above-described shade (movable shade) of the vehicle lighting fixture described in JP-A-2006-341696 is rotatably supported inside an attachment frame, the attachment frame has a generally tubular shape and is attached to the front end part of a reflector, and a light projection lens (projection lens) is attached to an opening on the front surface.
In general, the attachment frame having the substantially tubular shape is formed by aluminum die casting or the like in which a melted aluminum alloy is injected into a molding die and integrally molded. In recent years, further weight reduction is required in order to improve fuel efficiency, but the weight reduction by the aluminum die casting has its limits.